This invention pertains to a pulsating signal generator for the production of n systems of polyphase voltages with n phases, in which the resulting pseudo-sinusoidal voltages of each of the n systems are modulated in amplitude to a predetermined, fixed or variable, pulsation .epsilon., and staggered by 2.pi./n among themselves.
The interference between the two sinusoidal voltages of frequency f.sub.1, and f.sub.2, or pulsations .omega..sub.1, and .omega..sub.2 (where .omega..sub.1 =2.pi.f.sub.1 and .omega..sub.2 =2.pi.f.sub.2), and with different amplitudes U.sub.1, and U.sub.2, is a well known phenomenon, currently used in radio, in the technique of synchroscopes, in transmitters, etc.
This phenonmenon may be summarized by the following equation: EQU U(t)=U.sub.1 sin .omega..sub.1 t+U.sub.2 sin .omega..sub.2 t=2U.sub.o cos (.epsilon.t) sin (.omega.t)+2e sin (.epsilon.t) cos (.omega.t) (1)
in which
.omega..sub.1 =.omega.+.epsilon. PA1 .omega..sub.2 =.omega.-.epsilon.and PA1 U.sub.1 =U.sub.o +e PA1 U.sub.2 =U.sub.o -e
with an average pulsation .epsilon. and an average voltage of the component sinusoidal voltages U.sub.o. The general characteristics of the voltage resulting from the "pulsating" signal U(t) are shown in FIG. 1 by the solid line C.sub.1. Of course, if two systems of polyphase voltages are connected in series, phase to phase, n voltages analogous to that of equation (1) are obtained within the same envelope, but staggered by 2.pi./n being the number of phases of each system of voltages. FIG. 2 represents the graphs of these voltages which are as follows: ##STR1## (Two triphase systems will be considered hereinafter in an example of a generator according to this invention).
Furthermore, if the differential voltage e=0, that is if U.sub.1 =U.sub.2 =U.sub.o, the resulting voltage U(t)=2U.sub.o cos .epsilon.t sin .omega.t, may be described as a "pseudo-sinusoidal" voltage of pulsation .epsilon., and of variable amplitude 2U.sub.o cos .epsilon.t. The same is true for the resulting voltages of the two polyphase systems placed in series, phase to phase, and previously described. This latter series polyphase system corresponds to the situation illustrated by the graph FIG. 3a, and described mathematically as follows: ##EQU1##
In addition, circular permutations of the phases of the second polyphase system, in relation to the first one, results in n groups of voltages with a general aspect similar to that of the frist group, but the respective envelopes of which are staggered among themselves. Thus it can be seen in FIG. 3a and the corresponding equation above, and FIGS. 3b, and 3c and their corresponding equations below that there are three groups of U.sub.a, U.sub.b and U.sub.c voltages with: ##EQU2## The vectorial representation of these equations is given on FIGS. 4a, 4b, and 4c, in which the system U.sub.11, U.sub.12, and U.sub.13 rotates at the speed (.omega.t+.epsilon.t) and the system U.sub.21, U.sub.22, and U.sub.23 rotates at the speed (.omega.t-.epsilon.t). The resulting voltages (U.sub.a.sbsb.1, U.sub.a.sbsb.2, U.sub.a.sbsb.3), (U.sub.b.sbsb.1, U.sub.b.sbsb.2, U.sub.b.sbsb.3), and (U.sub.c.sbsb.1, U.sub.c.sbsb.2, U.sub.c.sbsb.3) form three "pseudo-triphase" systems of variable amplitudes respectively equal to U.sub.A.sbsb.o =2U.sub.o cos .epsilon.t, U.sub.B.sbsb.o =2U.sub.o cos ##EQU3##
This invention has as its primary object to provide a novel appropriate means of utilizing this "pulsating" phenomenon, especially in order to obtain a system of polyphase voltages at a given, constant or variable, frequency, f, and corresponding to the pulsation .epsilon. from an electric generator producing voltages responding to the previously described equations (3, 4, 5).
A more specific object of this invention is to provide a novel pulsating signal generator permitting the production of systems of polyphase voltages at n phases responding to n systems of equations of the kinds (3) to (5) above.
It is known that pulsating signal generators of this kind in which two alternators are being used, each with its own frequency. However, this device is costly and cumbersome taking into consideration the need to use two separate rotating machines. This invention aims more particularly at permitting the realization of a pulsating signal generator in a manner altogether simple, economical and efficient. These and other objects of the invention are obtained through a pulsating signal generator which according to the invention, preferably includes a rotating double homopolar machine including a double homopolar stator circuit provided wth two armatures, each including a system of polyphase windings with n independent circuits per phase, each circuit of each phase of the first armature being connected in series with one of the circuits of a phase of the second armature, in such a way as the circuits of the second armature connected in series with the circuits of a same phase of the first armature will all belong to different phases, determined by circular permutations. The pulsating signal generator includes a rotor with a rotating magnet divided into two half-rotors at right angle with an airgap. An induction coil for excitation of the armature is disposed concentric the axis of the rotor in order to produce a magnetic flux in the two armatures. In addition there is provided means for driving the two half-rotors at speeds .omega..sub.1, and .omega..sub.2 different one from the other and which are such that the half-difference of the speeds (.omega..sub.1 -.omega..sub.2 /2) is equal to .epsilon..
The generator according to the invention is especially compact since it includes a single frame and a common stator, while it permits a great flexiblity of operation.
According to a particular form of the invention, the half-rotors are driven into rotation by means of a differential device which is itself driven by a single drive.
Another advantageous feature of the generator of one embodiment is the addition of at least one auxiliary excitation coil, concentric to the axis of the rotor and permitting control of the real flux in the two armatures, thereby achieving regulation of the flux and balancing of the rotor. Other characteristics and advantages of the invention will become apparent to one skilled in the art on reading the following detailed description of some specific forms of the invention given only as non-limitating examples with reference to the attached drawings.